The mystery 'shadow zone' in the Pacific Ocean that hasn't moved in more than 1,500 years due to the unique shape of the seabed and its impact on currents

The 'shadow zone' covers an area 3,700 by 1,250 (6,000 by 2,000 km) where the North Pacific meets the Indian Ocean, between 0.6 and 1.5 miles (one and 2.5 km) below the surface

From DailyMail by Tim Collins

The 'shadow zone' covers an area 3,700 by 1,250 miles (6,000 by 2,000 km)
It is found between 0.6 and 1.5 miles (1 and 2.5 km) beneath the ocean's surface
Experts used computer modelling of ocean currents to work out how it formed
It revealed the shape of the ocean floor prevents any upward currents forming

In the North Pacific, way below the surface, hangs water that hasn't seen the sun in a millennium.
Tibor Kranjec / Eyeem

A mysterious patch of water in the Pacific Ocean hasn't touched the surface since the fall of the Roman empire.
Experts used computer modelling of deep sea currents to reveal the reason why the vast 'shadow zone' has remained near stagnant for around 1,500 years.
They found that it sits in between layers of water with currents driven by heat from the Earth below and whipped up by wind above.

The unique shape of the ocean floor means that upwards currents don’t reach high enough to push the layer upwards, leaving it in a no man’s land between the two.

A mysterious patch of water in the Pacific Ocean hasn't touch the surface since the fall of the Roman empire.

Experts found that it sits in between geothermal driven currents below and wind driven currents above

An international team of researchers, including the University of New South Wales (UNSW) and Stockholm University, studied the strange region, between 0.6 and 1.5 miles (one and 2.5 km) down.
It covers an area 3,700 by 1,250 miles (6,000 by 2,000 km), where the North Pacific meets the Indian Ocean.

Carbon dating has previously been used to identify its age and location, but scientists didn't understand what caused it to form.
By including the shape of the ocean floor in their simulation, the team was able to measure its impact on the movement of currents.
They found that water at the bottom of the ocean, heated by geothermal energy deep within the planet, was unable to rise above 1.5 miles (2.5km) below the surface.

C. de Lavergne et al./ Nature, 2017

Instead of travelling upwards, currents loop back on themselves horizontally, leaving the layer directly above untouched.
Dr Casimir de Lavergne, lead author from UNSW, said: 'Carbon-14 dating had already told us the most ancient water lied in the deep North Pacific.
'But until now we had struggled to understand why the very oldest waters huddle around the depth of 1.2 miles (2km).
'What we have found is that at around 1.2 miles (2km) below the surface of the Indian and Pacific Oceans there is a 'shadow zone' with barely any vertical movement that suspends ocean water in an area for centuries.'

While the researchers have unlocked one part of the puzzle, their results also have the potential to tell us much more.
The lack of contact with the ocean's surface means oxygenation of the zone is very low.
That means marine life is restricted, but not completely absent.

It is hoped that the research could help scientists better understand the capacity of the oceans to absorb heat trapped by rising greenhouse gases.
'When this isolated shadow zone traps millennia old ocean water it also traps nutrients and carbon,' added fellow author from Stockholm University, Dr Fabien Roquet.
'[These factors] have a direct impact on the capacity of the ocean to modify climate over centennial time scales.'

The full findings of the study were published in the journal Nature.

Links :

• SMH : Answers to the world's 'oldest water' found in the deep blue north Pacific
• Newsweek : Mystery 'sahdow patch' in Pacific hasn't moved for 1000 years and scientists know why
• Phys : How a 'shadow zone' traps the world's oldest ocean water
• ScienceMag : How A ‘Shadow Zone’ Traps The World’s Oldest Ocean Water

Antarctica's warm underbelly revealed

Hotspots are located under West Antarctica; in contrast, the East is broadly relatively cold 

From BBC by Jonathan Amos

This is the best map yet produced of the warmth coming up from the rocks underneath the Antarctic ice sheet.

Measurements suggest a hot plume of mantle rock below West Antarctica.
(Helene Seroussi et al./JGR Solid Earth; Business Insider) 

This "geothermal heat flux" is key data required by scientists in order to model how the White Continent is going to react to climate change.
If the rock bed's temperature is raised, it makes it easier for the ice above to move.
And if global warming is already forcing change on the ice sheet, a higher flux could accelerate matters.

The map was made by researchers at the British Antarctic survey and is published in the journal Geophysical Research Letters.
"The heat coming from the Earth’s interior is important to understand the overall conditions that control the dynamics at the base of the ice sheet and hence the ice flow,” explained Yasmina Martos, currently affiliated to the US space agency.
"If this heat flux is elevated, the ice base can melt and produce water that acts as a sliding film.
"One result of our study is that the heat flux is higher underneath West Antarctica, where more ice is currently melting, than underneath East Antarctica.
"Even a little melting at the base helps the ice sheet to slide faster.
We also identified areas of low heat flux, which will help stabilising the ice sheet," she told BBC News.

 A map of Antarctica shows where Totten Glacier is.

Map: Chad A. Greene, University of Texas Institute for Geophysics, 2017

The West contributes most to sea level rise currently, but this is a consequence of warm ocean water eroding glacier fronts - not from the interior ice sheet being melted by underlying warm rock
No-one has actually drilled through the kilometres of ice in Antarctica to take the temperature of the bed.

Instead, the BAS team inferred the likely warmth of rocks from their magnetism.
This property can be sensed by instruments flown across the surface of the ice sheet by planes.

What happens next is a smart calculation.
Scientists know the temperature (580C) at which hot minerals lose their magnetism, so if they can gauge how close to the rock-ice interface this occurring then they have a means of estimating the heat flux.
The new map is said to represent a 30-50% improvement on previous efforts.

Surface wind causes warm water to upwell at the continental shelf break, the warm water melts Totten Ice Shelf from below, and the glacier responds by speeding up.

Chad A. Greene, University of Texas Institute for Geophysics, 2017

It supports - but with far more detail - the established idea that East and West Antarctica are very different provinces.
The East is a giant chunk of old, cold continental crust.
The West, however, underwent recent rifting in the Cretaceous (100 million years ago) that has pulled it apart.
"This rifting has thinned the crust and brought hot material from deep down in the Earth - from hundreds of km down - to within 100km or so, or even maybe less, of the rock surface," said co-author Tom Jordan.
"It confirms what you would expect from the sparse, exposed geology in West Antarctica where we have volcanoes."

One of the great advances in polar science in the past decade is the recognition that there is a really extensive hydrological network under the ice sheet.
Rivers of water feed huge subglacial lakes that fill and burst their banks periodically. Satellites see the top of the ice sheet heave and relax when this happens.

Illustration of flowing water under the Antarctic ice sheet.

Blue dots indicate lakes, lines show rivers.

Marie Byrd Land is part of the bulging "elbow" leading to the Antarctic Peninsula, left center.

Credit: NASA / NSF/Zina Deretsky

Any projections of future change in Antarctica and its contribution to sea level rise through the loss of ice have to take this basement hydrology into account, and the variations in geothermal heat flux are a critical part of the overall picture.
One research project that will see an immediate benefit from the map’s data is the quest to drill the oldest ice on the continent.
Europe, America, China and others are seeking a location where they can collect a core of frozen material that contains a record of past climate stretching back at least 1.5 million years.
This information - about historic atmospheric conditions including carbon dioxide levels - can be deciphered from tiny air bubbles trapped in the ice.

 Map of antarctic ice flow speeds (2011).

(NASA's Goddard Space Flight Center Scientific Visualisation Studio)

But the whole endeavour depends on the base of the ice sheet being undisturbed.
Places with a warm rock underbelly are therefore to be avoided, obviously.
"It is very exciting to see the implications this new heat map has for many communities, including new generations of ice sheet and sea level models," said Dr Martos.
"I am very glad we are contributing an important aspect at unprecedented detail. The Earth’s interior has a lot to tell us in terms on how the ice behaves."

Links :

• BBC : Decoding Antarctica's response to warming /  Shells record Antarctic glacier retreat /  Big ice melt scenarios 'not plausible' /  
• The Verge : East Antarctica’s biggest glacier lost ice because of warm water and strong winds
• Wired : For scientists predicting sea level rise, wind is the biggest unknown
• The Independant : Antarctica is being rapidly melted from below says Nasa, and it thinks it knows why 
• Scientific American : How Wind Might Nudge a Sleeping Giant in Antarctica
• The Conversation : Warm waters melting Antarctic ice shelves may have appeared for the first time in over 7,000 years 
• Business Insider : Hot rock under Antarctica may be melting some of its ice sheets from the bottom-up
• The Atlantic : A Photo Trip to Antarctica 

France & misc. SHOM layer update in the GeoGarage platform

5 new nautical raster charts added & 57 updated

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Norway NHS layer update in the GeoGarage platform

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Scientists warn of 'giant leap backward' at climate talks

@N_Hulot tweet

Hard to ignore 15000 scientists from 184 nations

who issue second warning to humanity on catastrophic climate change.

From NPR

Carbon dioxide emissions are set to rise this year after a three-year pause, scientists said at UN climate talks Monday, warning that "time is running out", even as White House officials used the occasion to champion the fossil fuels that drive global warming.

CO2 emissions, flat since 2014, were forecast to rise two percent in 2017, dashing hopes they had peaked, scientists reported at 12-day negotiations in the German city of Bonn ending Friday.
"The news that emissions are rising after a three-year hiatus is a giant leap backward for humankind," said Amy Luers, a climate policy advisor to Barack Obama and executive director of Future Earth, which co-sponsored the research.
Global CO2 emissions for 2017 were estimated at a record 41 billion tonnes.
"Time is running out on our ability to keep warming below two degrees Celsius (3.6 degrees Fahrenheit), let alone 1.5 C," said lead author Corinne Le Quere, director of the Tyndall Centre for Climate Change Research at the University of East Anglia.

In 1992, scientists warned that humans had to change or the Earth would become unlivable.
What's changed 25 years later?

The 196-nation Paris Agreement, adopted in 2015, calls for capping global warming at 2 C below pre-industrial levels.

With the planet out of kilter after only one degree of warming—enough to amplify deadly heatwaves, droughts, and superstorms—the treaty also vows to explore the feasibility of holding the line at 1.5 C.
"As each year ticks by, the chances of avoiding 2 C of warming continue to diminish," said co-author Glen Peters, research director at Center for International Climate Research in Oslo, Norway.
"Given that 2 C is extremely unlikely based on current progress, then 1.5 C is a distant dream," he told AFP.

The study identified China as the single largest cause of resurgent fossil fuel emissions in 2017, with the country's coal, oil and natural gas use up three, five and 12 percent, respectively.
Earth is overheating due to the burning of oil, gas and especially coal to power the global economy.

Sea ice as viewed from NASA's research aircraft in the Antarctic Peninsula region this month.Scientists warn that Earth is heading towards a dangerous 'tipping point' which could result in the disintegration of Antarctic ice sheets

'You're liars!'

That did not discourage US officials from the administration of President Donald Trump from making a case at the UN negotiations for "The Role of Cleaner and More Efficient Fossil Fuels and Nuclear Power in Climate Mitigation."
"Without a question, fossil fuels will continue to be used," George David Banks, a special energy and environment assistant to the US president told a standing-room only audience, citing projections from the International Energy Agency (IEA).
Faced with this reality, "we would argue that it's in the global interest to make sure that when fossil fuels are used, that it's as clean and efficient as possible."

Flanked by Francis Brooke from the office of Vice President Mike Pence, and senior representatives of American energy companies, Banks addressed a packed room where protesters shouted "you're liars!" and "there's no clean coal!".
Former New York mayor Michael Bloomberg, UN special envoy for cities and climate change, tweeted: "Promoting coal at a climate summit is like promoting tobacco at a cancer summit."
The US is the only country in the world that has opted to remain outside the Paris Agreement.

More than 15,000 scientists meanwhile warned that carbon emissions, human population growth, and consumption-driven lifestyles were poisoning the planet and depleting its resources.
"We are jeopardising our future," they wrote in a comment entitled "World Scientists' Warning to Humanity: A Second Notice," echoing a similar open letter from 1992.
It is "especially troubling" that the world continues on a path toward "potentially catastrophic climate change due to rising greenhouse gases from burning fossil fuels," they said.

Searches for somewhere dry to take shelter

Rainforest into savanna

"We have unleashed a mass extinction event, the sixth in roughly 540 million years."
Another group of scientists cautioned that rising global temperatures were bringing Earth ever closer to dangerous thresholds that could accelerate global warming beyond our capacity to rein it in.
"In the last two years, evidence has accumulated that we are now on a collision course with tipping points in the Earth system," Johan Rockstrom, executive director of the Stockholm Resilience Centre.

Some scientists, for example, have concluded that the planet's surface has already warmed enough—1.1 degrees Celsius (2.0 degrees Fahrenheit) on average—in the last 150 years to lock in the disintegration of the West Antarctic ice sheet, which holds enough frozen water to lift global oceans by six or seven metres.
It may take 1,000 years, but—if they are right—the ice sheet will melt no matter how quickly humanity draws down the greenhouse gases that continue to drive global warming.

Life.

It's the one thing that, so far, makes Earth unique among the thousands of other planets we've discovered.

Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean.

Rockstrom and colleagues identified a dozen such natural processes that could tip into abrupt and irreversible change.
An increase of 1-3 C, for example, would likely provoke the loss of Arctic summer sea ice, warm-water coral reefs, and mountain glaciers.
A degree or two more would see large swathes of the Amazon rainforest turn into savanna, and slow a deep-sea current that regulates weather on both sides of the northern Atlantic.
The International Union for Conservation of Nature (IUCN), meanwhile, released a report Monday showing that climate change now imperils one in four natural World Heritage sites, including coral reefs, glaciers, and wetlands—nearly double the number from just three years ago.

Links :

• Motherboard : 15000 Scientists From 184 Countries Are Warning Humankind We Are Screwed
• Newsweek : How to save humanity: 15,000 scientists urge action before 'vast human misery' takes over
• Washington Post : Thousands of scientists issue bleak ‘second notice’ to humanity 
• The Independant : 15,000 scientists give catastrophic warning about the fate of the world in new ‘letter to humanity'
• BBC : First CO2 rise in four years puts pressure on Paris targets
• NYTimes : The stakes in the Paris Climate Deal : What might other countries do ?